1. Field of the Invention
In heat engine power systems, especially those designed for military vehicular propulsion, it is the practice to maintain a design balance among all components of the system. Thus a vehicle carrying a heat engine power system is equipped with a fluid fuel heat engine having sufficient horsepower at the wheel contact points on the road to provide the desired performance characteristics. The power system carries a cooling subsystem which has the capacity to carry away the rejected heat of the heat engine under assumed conditions, but that subsystem is not designed to carry away the rejected heat that would be generated by a substantially larger engine.
In military equipment, such a design balance is likely to be closely engineered for optimum performance. For example, a personnel carrier, or a tank, must have the maximum mobility and maneuverability possible for its size and consistent with other necessary capabilities, and the stated equipment will not be provided with a cooling subsystem twice as big as needed to cool the propulsion engine in the equipment, because the extra weight of such an oversize cooling subsystem could be more usefully devoted to another man, more ammunition, more fuel, heavier armor, or the like.
It sometimes happens that the engines in equipment already in the field must, when rendered unserviceable, be replaced by somewhat larger engines (longer stroke, and/or larger bore, and therefore greater displacement) which fit in the available space and which also fit one or more larger lines of equipment. Use of the bigger engine in the smaller equipment overloads the cooling subsystem if the replacement engine is driven at wide-open throttle, especially when the equipment is run at high ambient air temperatures.
2. The Prior Art.
The quick and easy solution to the problem of cooling subsystem overload is to place a baffle plate or some other restriction in the fuel line, as for example in the intake manifold, to limit the power output of the larger engine to original levels. Such an expedient does prevent overloading of the cooling subsystem. The disadvantage of such a solution is that it limits power output at all times, even when ambient temperatures are low.
It therefore is desirable to have a heat engine power system which enables the users to take advantage of maximum engine horsepower as long as such operation can take place without serious risk of damage to some part of the power system. As an example, when ambient air temperatures are low, the cooling subsystem which uses ambient air to cool a circulated liquid coolant will have a substantially greater capacity to carry away the rejected heat of the heat engine than when ambient air temperatures are high, and the larger, more powerful, engine can be operated at maximum horsepower in such circumstances (low ambient temperature). This gives the troops greater mobility and greater striking power than a power system forced to operate at restricted power all the time. At the same time, the system which we propose here offers as much protection against overload damage as can be afforded with conventional safeguards such as a fixed restriction, and without the drawbacks.